Tabs and style sheets

I found some info on the doc site about customizing tabs.
I tried overriding some styles:
.ui-tabs {
background-color: #00FF00;
}
.ui-tabs-nav {
background-color: #0000FF;
}
.ui-tabs-panel {
background-color: #FF00FF;
}
Only the .ui-tabs rule took affect, and there is
a band of white through the center when the content
is long enough:
http://register.rcsreg.com/regos-1.0/tab/splash.html
Am I missing more customization documents somewhere?
Do I get to do anything besides tweak a couple of colors?
Thanks!
Tobiah